Manufacture of celluloid and like balls



Dec. 24, 1935. Y J M JAQUES 2,025,455

MANUFACTURE OF CELLULOID AND LIKE BALLS Filed July 25, 1935 Ivw nZZr Jofin M Jag Law i F v, Q a

Patented Dec. 24, 1935 UNITED STATES PATENT oFFIeE John Minnison Jaques, London, England Application July 25, 1935, Serial No. 33,173 In Great Britain July 10, 1934 Claims. (01. 18-56) This invention relates to the manufacture of balls of celluloid and the like such as are used in the game of table tennis (also known under the registered trade-mark Ping Pong) and in similar games.

Such balls are usually made of celluloid and the ordinary method of making them is to stamp out two halves of the ball i'rom celluloid sheeting while hot, apply acetone to the edges of the stampings and to fit and seal them together to form a closed rough sphere with a median seam where the edges overlap. The rough sphere is then enclosed in a split mould, the exact spherical shape of the ball to be produced and the mould is closed and immersed in hot water so that the expansion of the air within the ball blows it out to the shape of the mould. The mould is then allowed to cool and the ball is removed.

In carrying out the above described method, however, it has been found impossible to produce a truly spherical ball since the double width of material at the overlapped edges of the two halves of the ball causes a shrinkage when cooling after the blowing process which has the efiect of making the seam diameter of the ball approximately one ten-thousandth of an inch less than the diameter at right angles thereto.

The present invention has for its object to provide an improved method whereby a much closer 30 approximation to a truly spherical ball can be produced.

According to the invention the ball is made as a closed rough sphere with an overlapping seam by the method hereinbefore described or by any other suitable method but the mould used for blowing the ball is not a true sphere. The parts of the mould are so formed that when fitted together that diameter which corresponds to the seam of the ball is larger than the diameter at right angles thereto by an amount which is approximately equal to the amount of shrinkage at the seam diameter of the ball which takes place after the ball has been blown and cooled.

The rough sphere is then placed in the mould 4.5 in such a manner that its seam diameter registers exactly with the larger seam diameter of the mould and then the ball is blown in hot water as usual to fit the mould. Thus the ball is overblown at the seam diameter by an amount equal 50 to the shrinkage along that diameter which takes place when the ball cools. Thus on cooling the closest possible approximation to a truly spherical ball is obtained.

To enable the invention to be fully understood 55 it will now be described by reference to the accompanying drawing which shows a sectional elevation of one form of ball mould formed for carrying out the invention.

In the example illustrated the mould is made in halves l, 2 provided with vents 3 to allow the escape of air during blowing in the usual manner. The mould when fitted together is not a true sphere the diameter A which corresponds to the seam oi the ball is larger than the diameter B at right angles thereto by an amount which is approximately equal to the amount of shrinkage at the seam diameter oi the ball which takes place after the ball has been blown and cooled.

Preferably the ball is held in the exact position in the mould by some such fixative as petroleum jelly so that it cannot move and will register its seam line diameter exactly with the seam line joint in the mould, which as explained is the larger diameter A. The mould is used to form a ball in the manner hereinbeiore described. 20

It has been found when working with the ordinary celluloid balls now on the market that the seam shrinkage is approximately one to two tenthousandth parts of an inch but it will be understood that the shrinkage of other types of celluloid balls can be measured and the mould made accordingly for the purpose of carrying out this invention.

While it is convenient to employ a mould divided into halves it is obvious that the mould may be divided into any other suitable number of parts.

I claim:

1. In the method of manufacturing balls of celluloid or the like as hereinbefore referred to the employment of a ball mould the diameter of which corresponding to the seam of the ball is larger than the diameter at right angles thereto by an amount which is approximately equal to the amount of shrinkage at the seam diameter of the ball which takes place after the ball has been blown and cooled.

2. In the method according to claim 1 the use of a. fixative for holding the rough ball in the exact position in the mould so that it cannot move and will register its seam line diameter exactly with the larger diameter in the mould.

3. In the method of manufacturing balls of celluloid or the like the use of a mould made in halves so formed that when fitted together the joint corresponds to the seam of the ball and the diameter of the mould at said joint is larger than the diameter at right angles. thereto by an amount Which is approximately equal to the amount of 55 shrinkage at the seam diameter which takes place after the ball has been blown and cooled.

4. The method of manufacturing a ball of celluloid or the like which consists in securing two halves of a ball together with overlapping edges forming a medial seam so that a closed rough sphere is obtained, then enclosing the sphere in a split mould which is not truly spherical but having that diameter which corresponds to and registers with the seam of the sphere larger than the diameter at right angles thereto by an amount approximately equal to the amount of shrinkage which takes place after the sphere has been blown and cooled, heating the mould so that the sphere is blown out to fit the mould and then allowing it to cool whereby an approximately spherical ball is obtained.

5. For use in manufacturing celluloid and like balls a split ball mould which is not a true sphere, one diameter of the mould being larger than the diameter at right angles thereto. by an amount which is approximately equal to the amount of shrinkage at the seam diameter of the ball to be made which takes place after the ball has been blown and cooled.

JOHN MINNISON JAQUES. 

